1. Field of the Invention
The present invention relates to a signal line correction method and apparatus for performing a signal line correction on a radiation image signal read out from a radiation image detector.
2. Description of the Related Art
Various types of radiation image detectors that receive radiation transmitted through a subject to record a radiation image of the subject are proposed and put into practical use in the medical and other industrial fields.
The radiation image detectors include, for example, radiation image detectors using amorphous selenium that generate charges by receiving radiation and as such radiation image detectors, a so-called optical readout type and a TFT readout type are proposed.
As for the optical readout type, for example, a radiation image detector having the following layers stacked in the order listed below is proposed: a first electrode layer that transmits radiation representing a radiation image; a recording photoconductive layer that generates charges by receiving the radiation transmitted through the first electrode layer; a charge transport layer that acts as an insulator against charges of one polarity of those generated in the recording photoconductive layer and as a conductor for charges of the other polarity; a readout photoconductive layer that generates charges by receiving readout light; and a second electrode layer that includes a transparent linear electrode that transmits the readout light and an opaque linear electrode that blocks the readout light.
As for the TFT readout type, for example, a radiation image detector having the following stacked on top of each other is proposed: an upper electrode to which a voltage is applied; a semiconductor layer that generates charges by receiving radiation; and an active matrix substrate that includes multiple of pixels, each having a storage capacitor for storing charges generated in the semiconductor layer and a TFT switch for reading out the charges stored in the storage capacitor, disposed two-dimensionally, with scanning electrodes, through which control signals for switching ON/OFF the TFT switches are transmitted, and data electrodes, through which charge signals read out from the storage capacitors via the TFT switches flow out, provided in a grid pattern.
Here, in such radiation image detectors described above, the linear electrodes or data electrodes (hereinafter, referred to as “signal lines”) through which charge signals flow out may possibly have a fault, such as a breakage or the like. Such a fault poses a problem that the intensity of a signal read out by a signal line adjacent to the faulty signal line is changed due to a response delay. Further, a charge leaks from the faulty signal line to an adjacent signal line, causing a problem that the intensity of a signal read out by the adjacent signal line is changed.
The signal lines of radiation image detectors described above are connected to a readout circuit having charge amplifiers for detecting signals flowing out to the respective signal lines, and the like. Then, in the readout circuit, the outputs of the charge amplifiers are sequentially switched by a multiplexer and connected to an A/D converter, whereby radiation image signals corresponding to the respective signal lines are sequentially read out.
There has also been a problem, however, that the intensity of a signal read out by a first target signal line in the readout circuit is changed due to a response delay.
Heretofore, when such a signal line fault as described above occurs, a signal read out from an abnormal signal line adjacent to the faulty signal line has been corrected by performing interpolation using a signal read out by a normal signal line adjacent to the faulty signal line as described, for example, in U.S. Patent Application Publication No. 20060132626.
Performance of the interpolation using the signal read out by the normal signal line adjacent to the faulty signal line, however, causes information of the signal read out by the abnormal signal line to be lost completely. In fact, the signal read out by the abnormal signal line is abnormal only in density, i.e., in a low frequency component and not in a high frequency component.
Further, for the signal read out by the first target signal line of the readout circuit, performance of interpolation using a signal of an adjacent signal line causes the same problem as described above.
In view of the circumstances described above, it is an object of the present invention to provide a signal line correction method and apparatus capable of reducing information loss of a radiation image.